Hot-Melt Adhesive Composition and Manufacturing Method Therefor

ABSTRACT

A hot melt adhesive composition is provided that includes: a diblock copolymer including a styrene-based monomer-derived unit and a conjugated diene-based monomer-derived unit; a triblock copolymer which is a coupled polymer of the diblock copolymer; and a crosslinked block copolymer including a crosslinking agent-derived crosslinked part crosslinked with two or more of the diblock copolymer and the triblock copolymer. The conjugated diene-based monomer-derived unit includes an isoprene-derived unit and an epoxidized isoprene rubber.

TECHNICAL FIELD Cross-Reference to Related Applications

The present application claims the benefit of priorities to KoreanPatent Application No. 10-2019-0124524 filed on Oct. 8, 2019 and KoreanPatent Application No. 10-2020-0098993 filed on Aug. 7, 2020, the entirecontents of which are incorporated herein as a part of thespecification.

TECHNICAL FIELD

The present invention relates to a hot melt adhesive compositionincluding a block copolymer composition and a method of preparing thesame.

BACKGROUND ART

A hot melt adhesive, which is an adhesive using a thermoplastic resin tobe melted by heat, thereby forming an adhesive surface, does not use avolatile solvent or the like unlike a conventional UV-curable adhesiveto emit less of a harmful substance upon curing, and thus, is preferredas an environment-friendly highly functional adhesive.

The hot melt adhesive is lower-priced than a UV-curable adhesive and ispresent in a liquid state at a high temperature, and thus, is easilyapplied and compressed on a substrate and an adherend, and then iscooled and solidified at room temperature within several seconds toexert adhesive strength, and thus, is easily used.

Since the hot melt adhesive is applied to an adherend in a melted stateand then cooled to form a hard phase having cohesiveness and creepresistance, the hot melt adhesive is widely used in various industrialfields of industry, such as, diapers or feminine hygiene products,manufacture of pressure sensitive adhesive electronic products such asindustrial tape or packaging tape, structural materials, and the like.

Since the hot melt adhesive includes a base resin, an additive, and thelike, phase separation and bleeding occur due to compatibility and thelike to decrease adhesive strength, a relatively high temperaturecondition is required during melting processing for adhesion due to highviscosity, and in particular, at the processing temperature condition assuch, problems such as viscosity change, odor generation, anddiscoloration may occur, and thus, a demand for a low-viscosity productis increased.

Accordingly, development of a hot melt adhesive which maintainslow-viscosity properties, may improve processing processability, and hasexcellent adhesive strength and thermal resistance and also excellentphysical properties after curing is demanded.

DISCLOSURE Technical Problem

The present invention was contrived for solving the problems of thebackground art, and the object of the present invention is to provide ahot melt adhesive composition which has a high softening point so thatit may be applied at a high temperature, and also may improve adhesion.

Technical Solution

In one general aspect, a hot melt adhesive composition includes: adiblock copolymer including a styrene-based monomer-derived unit and aconjugated diene-based monomer-derived unit; a triblock copolymer whichis a coupled polymer of the diblock copolymer; and a crosslinked blockcopolymer including a crosslinking agent-derived crosslinked partcrosslinked with two or more of the diblock copolymers and the triblockcopolymers, wherein the conjugated diene-based monomer-derived unitincludes an isoprene-derived unit and an epoxidized isoprene rubberrepresented by the following Chemical Formula 1:

In another general aspect, a method of preparing a hot melt adhesivecomposition includes: polymerizing a styrene-based monomer in thepresence of a hydrocarbon solvent and a polymerization initiator toprepare a styrene-based monomer block (S10); polymerizing thestyrene-based monomer block and isoprene to prepare a diblock copolymerincluding a styrene-based monomer-derived unit and an isoprene-derivedunit (S20); coupling two or more of the diblock copolymers and acoupling agent to prepare a triblock copolymer, thereby preparing ablock copolymer composition including the triblock copolymer and thediblock copolymer (S30); reacting a part of the isoprene-derived unitincluded in the diblock copolymer and the triblock copolymer and amixture of hydrogen peroxide and a carboxylic acid to substitute a partof the isoprene-derived unit with an epoxidized isoprene unit (S40); andcrosslinking two or more of the triblock copolymers and the diblockcopolymers including the epoxidized isoprene unit with a crosslinkingagent to prepare a crosslinked block copolymer (S50).

Advantageous Effects

The hot melt adhesive composition including a diblock copolymer, atriblock copolymer, and a crosslinked block copolymer thereof accordingto the present invention has improved performance required at a hightemperature such as high temperature stability and viscosity retentionproperties at a high temperature, simultaneously with improved adhesivestrength, by functionalizing a part of a conjugated diene-based monomerunit forming a conjugated diene-based monomer block of a copolymer withan epoxy group.

BEST MODEL

Hereinafter, the present invention will be described in more detail forbetter understanding of the present invention.

Since the present invention may be variously modified and may havevarious forms, it is to be understood that the present invention is notlimited to a specific disclosed form, but includes all of themodifications, equivalents, and substitutions within the spirit andtechnical scope of the present invention.

Meanwhile, the terms and words used in the description and the claims ofthe present invention are not to be construed limitedly as havinggeneral or dictionary meanings but are to be construed as havingmeanings and concepts meeting the technical ideas of the presentinvention, based on a principle that the inventors are able toappropriately define the concepts of terms in order to describe theirown inventions in the best mode.

In addition, the terms and the measurement methods used in the presentinvention may be construed as defined in the following, unless otherwisestated.

Meanwhile, the term, a “monomer-derived repeating unit” or a“monomer-derived unit” in the present invention may refer to a componentor a structure resulting from a monomer, or the material itself, or mayrefer to a unit which is formed in a polymer by the monomer introducedparticipating a polymerization reaction during polymerization.Furthermore, not only the case in which two or more monomer-derivedunits are repeated but also the case in which the number ofmonomer-derived unit is one may be expressed as the monomer-derivedrepeating unit.

The term “block” in the present invention represents a form of a polymerchain formed by block polymerizing monomers, and may refer to a form inwhich a plurality of monomer-derived units are continuously connected.For example, a styrene-based monomer block may refer to a polymer chainformed by block polymerization of a styrene-based monomer or an assemblyof a plurality of styrene-based monomer-derived units. The term “polymerblock” in the present invention may refer to a bundle of polymer chainsformed by block polymerization of a monomer.

A hot melt adhesive composition according to an exemplary embodiment ofthe present invention may include a diblock copolymer, a triblockcopolymer, and a crosslinked block copolymer in a crosslinked form oftwo or more thereof by a crosslinking agent. More specifically, the hotmelt adhesive composition according to an exemplary embodiment of thepresent invention may include a diblock copolymer including astyrene-based monomer-derived unit and a conjugated diene-basedmonomer-derived unit, a triblock copolymer which is a coupled polymer ofthe diblock copolymer, and a crosslinked block copolymer including acrosslinking agent-derived crosslinked part crosslinked with two or moreof the diblock copolymers and the triblock copolymers.

The diblock copolymer is a diblock copolymer including a styrene-basedmonomer-derived unit and a conjugated diene-based monomer-derived unit,and the conjugated diene-based monomer-derived unit may include anisoprene-derived unit and an epoxidized isoprene unit represented by thefollowing Chemical Formula 1:

More specifically, the diblock copolymer may be a diblock copolymerwhich includes a styrene-based monomer block (S) including astyrene-based monomer-derived unit and a conjugated diene-based monomerblock (I) including an isoprene-derived unit, in the form of (S)-(I-EI)in which a part of the isoprene-derived unit is functionalized with anepoxy group to be substituted by an epoxidized isoprene unit (EI)represented by Chemical Formula 1.

The triblock copolymer is a coupled polymer prepared by a couplingreaction of two or more diblock copolymers, and representatively, may bea triblock copolymer in the form of (S)-(I-EI)-(S). Meanwhile, thetriblock copolymer may further include a coupling agent-derived unitbetween the conjugated diene-based monomer block (I-EI) and thestyrene-based monomer block (S) depending on a coupling agent or acoupling manner.

Meanwhile, the crosslinked block copolymer is a block copolymer which isa crosslinked block copolymer in which two or more of the diblockcopolymers and the triblock copolymers are crosslinked by a crosslinkingagent, and may include a crosslinking agent-derived crosslinked part ina crosslinked area of the crosslinking agent with the diblock copolymeror the triblock copolymer.

The crosslinking agent includes two or more functional groups which arecrosslinkable with the epoxidized isoprene unit represented by ChemicalFormula 1 included in the triblock copolymer and the diblock copolymer,and may include a hydroxyl group or an amine group at both ends of thecrosslinking agent. The crosslinking agent may be polyalkylene glycol,alkylene glycol, or alkylene diamine, and specifically, may bepolyethylene glycol or ethylene glycol.

A styrene-based monomer for forming the styrene-based monomer-derivedunit may be styrene, alpha-methylstyrene, para-methylstyrene, vinyltoluene, vinyl naphthalene, para-butyl styrene, or a combinationthereof, and specifically styrene.

The styrene-based monomer-derived unit may be produced by polymerizationof the styrene-based monomer, and the styrene-based monomer-derived unitincluded in the hot melt adhesive composition may be included at 10 to20 parts by weight, specifically 13 to 18 parts by weight, based on atotal of 100 parts by weight of the block copolymers including thediblock copolymer and the triblock copolymer.

Since a glass transition temperature (Tg) value of the styrene-basedmonomer is higher than room temperature, the styrene-based monomer mayform a segment unit having a relatively hard nature in the copolymer.Therefore, when a content of the styrene-based monomer-derived unit is10 parts by weight or more, mechanical physical properties such ashardness of the hot melt adhesive composition including thestyrene-based monomer-derived unit may be improved, and simultaneouslythermal resistance may be maintained. In addition, when the content ofthe styrene-based monomer-derived unit is 20 parts by weight or less, anexcessive viscosity increase of the hot melt adhesive composition may besuppressed to increase processability, and simultaneously a problem ofdecreased adhesive strength may be prevented.

Meanwhile, as described above, in the conjugated diene-basedmonomer-derived unit of the present invention, it is more advantageousfor the conjugated diene-based monomer to include isoprene than toinclude 1,3-butadiene, in terms of adhesion performance of implementinghigh adhesive property and peel strength as an adhesive blend.

Furthermore, according to an exemplary embodiment of the presentinvention, in the hot melt adhesive composition including the conjugateddiene-based monomer-derived unit in which a part of the isoprene-derivedunit is substituted by an epoxidized isoprene unit represented byChemical formula 1, a phenomenon in which a viscosity of an adhesive isdecreased when storing the composition at a high temperature for a longtime is prevented, thereby maintaining desired adhesion properties at ahigh temperature for a longer time. Thus, high thermal stability andgood adhesive property may coexist.

From this point of view, the epoxidized isoprene unit included in thehot melt adhesive composition may be included at 0.5 to 5 parts byweight, specifically 1 to 3 parts by weight, based on a total of 100parts by weight of the isoprene-derived unit and the epoxidized isopreneunit. When a content of the epoxidized isoprene unit is 5 parts byweight or less, based on a total of 100 parts by weight of theisoprene-derived unit and the epoxidized isoprene unit, viscosity iseven increased during storing at a high temperature, so thatdeterioration of storage and high temperature storage properties may beprevented. Meanwhile, when the content of the epoxidized isoprene unitis 0.5 parts by weight or more, based on a total of 100 parts by weightof the isoprene-derived unit and the epoxidized isoprene unit, adecrease in viscosity of the adhesive during storage at a hightemperature for a long time is prevented.

Meanwhile, the diblock copolymer may be included at 15 to 25 parts byweight, based on a total of 100 parts by weight of the diblock copolymerand the triblock copolymer. According to an exemplary embodiment of thepresent invention, the triblock copolymer may be prepared by performinga coupling reaction on the diblock copolymer including the styrene-basedmonomer-derived unit and the conjugated diene-based monomer-derivedunit, and in this process, a diblock copolymer which does notparticipate in the coupling reaction may remain and be included in thehot melt adhesive composition. That is, the hot melt adhesivecomposition of the present invention may include a triblock copolymerand a diblock copolymer which remains without participating in thecoupling reaction.

Meanwhile, when a content of the diblock copolymer is within the range,viscosity may be appropriately increased and excellent thermalresistance properties may be implemented.

Meanwhile, the triblock copolymer according to an exemplary embodimentof the present invention may be a coupled polymer of the diblockcopolymer, and an example of the coupling agent may be a silanederivative such as dimethylchlorosilane, tetrachlorosilane,dimethyldiethoxysilane, dimethyldimethoxysilane, tetraethoxysilane, andtetramethoxysilane.

The hot melt adhesive composition according to an exemplary embodimentof the present invention may further include a blend for a hot meltadhesive of one or more selected from the group consisting of atackifier, a plastic oil, and an antioxidant.

A block copolymer including the diblock copolymer, the triblockcopolymer, and the crosslinked block copolymer may be included at 10 to40 parts by weight, based on a total of 100 parts by weight of the hotmelt adhesive composition.

The tackifier included in the hot melt adhesive composition may includeany one or more of an at least partially hydrogenated rosin ester-basedcompound and an at least partially hydrogenated dicyclopentadiene-basedpolymerized petroleum resin. Herein, a rosin has a concept including allof an abietic acid, a dehydroabietic acid in which hydrogen is removedfrom an abietic acid, and a dihydroabietic acid or a tetrahydroabieticacid to which two or four hydrogens are added, and the abietic acid andthe dihydroabietic acid to which two hydrogens are added are used tohave a concept of including all various isomers, depending on a positionof a double bond.

The rosin ester-based compound is formed by reacting a carboxyl group ofan abietic acid with an OH group of alcohol or polyol to be esterified,based on the abietic acid described above or a hydrogenated abietic acidstructure, and this also includes all esterified products of naturalrosin or modified rosin. The alcohol or polyol is an aliphatic alcoholhaving 1 to 20 carbon atoms, may be in the form of monoalcohol, diol,triol, tetraol, or pentaol, and more specifically, for example, may bemethanol, ethanol, glycerol, ethylene glycol, diethylene glycol,pentaerythritol, or the like. When polyol is used, the abietic acid maybe esterified with an entire or a part of a hydroxyl group of polyol,and thus, monoester, divalent ester such as diester, ternary ester, orquaternary ester may be formed.

Meanwhile, the dicyclopentadiene-based polymerization petroleum resinmay refer to a petroleum resin including C9-dicyclopentadiene preparedfrom C5, that is, a cyclopentadiene oil, produced as a by-product in anaphtha cracking process in which naphtha obtained by crude oil refiningis decomposed at a high temperature.

The cyclopentadiene produced in the naphtha cracking process is, in mostcases, dimerized to be present as a dicyclopentadiene structure, and thecyclopentadiene and the dicyclopentadiene as the dimer thereof may bemutually converted to each other by a Diels-Alder reaction and aretro-Diels-Alder reaction, and in particular, the cyclopentadiene maybe polymerized into the dicyclopentadiene by thermal polymerization orcatalyst polymerization. Therefore, the expression that the tackifierused in the present invention includes a partially-hydrogenateddicyclopentadiene-based polymerized petroleum resin may mean that atleast a part of dicyclopentadiene of the dicyclopentadiene-basedcompound included in the dicyclopentadiene-based polymerized petroleumresin described above is hydrogenated so that both dicyclopentane anddicyclopentadiene are included.

According to an exemplary embodiment of the present invention, thetackifier may be included at about 200 to about 400 parts by weight orabout 250 to about 350 parts by weight, based on a total of 100 parts byweight of the block copolymers including the diblock copolymer, thetriblock copolymer, and the crosslinked block copolymer. When thetackifier is included too little, a tackifying effect is insignificant,so that adhesion-related physical properties are not sufficientlyexhibited in the hot melt adhesive composition, and when too much of thetackifier is included, cohesion of an adhesive component is decreased,so that in this case also, adhesion-related physical properties may bedeteriorated.

Furthermore, the plastic oil included in the hot melt adhesivecomposition may include a petroleum-based mineral oil. Thepetroleum-based mineral oil is a liquid by-product produced in a processof refining crude oil into petroleum and also called liquid paraffin andrepresentatively, includes a paraffinic oil based on n-alkane, anaphthenic oil based on cycloalkane, and an aromatic oil based on anaromatic hydrocarbon, and in the present invention, the petroleum-basedmineral oil has a concept of including both the oils described above andmodified oils thereof. According to an exemplary embodiment of thepresent invention, the petroleum-based mineral oil is preferably aparaffinic oil, and more preferably, a white oil which is modified byhydrotreatment and/or dewaxing in the presence of a catalyst, or thelike.

Meanwhile, the plastic oil may be included at about 50 to about 150parts by weight, preferably about 70 to about 130 parts by weight, orabout 90 to about 110 parts by weight, based on a total of 100 parts byweight of the block copolymers including the diblock copolymer, thetriblock copolymer, and the crosslinked block copolymer. When a contentof the plastic oil is too low, flowability and low-temperatureprocessability may be deteriorated, and when the content of the plasticoil is too high, viscosity is excessively increased to ratherdeteriorate adhesion performance.

In addition, the hot melt adhesive composition according to an exemplaryembodiment of the present invention may further include an additive suchas a photostabilizer, a filler, and a UV absorber known in the art.These additives may be included at about 0.1 to about 10% by weight,based on the entire hot melt adhesive composition, in terms ofpreventing deterioration of adhesive physical properties,processability, and mechanical physical properties after adhesion.

Meanwhile, according to an exemplary embodiment of the presentinvention, an adhesive member including a substrate and an adhesivelayer formed on at least one surface of the substrate by the hot meltadhesive composition according to an exemplary embodiment of the presentinvention, is provided.

The adhesive member may be in the form of a film, a tape, or the like,and the substrate may be a film having one layer or a laminationstructure of two or more layers, or the like.

A method of preparing a hot melt adhesive composition according to anexemplary embodiment of the present invention will be described.

The method of preparing a hot melt adhesive composition of the presentinvention may include: polymerizing a styrene-based monomer in thepresence of a hydrocarbon solvent and a polymerization initiator toprepare a styrene-based monomer block (S10), polymerizing thestyrene-based monomer block and isoprene to prepare a diblock copolymerincluding a styrene-based monomer-derived unit and an isoprene-derivedunit (S20), coupling two or more of the diblock copolymers and acoupling agent to prepare a triblock copolymer, thereby preparing ablock copolymer composition including the triblock copolymer and thediblock copolymer (S30), reacting a part of the isoprene-derived unitincluded in the diblock copolymer and the triblock copolymer and amixture of hydrogen peroxide and a carboxylic acid to substitute a partof the isoprene-derived unit with an epoxidized isoprene unit (S40), andcrosslinking two or more of the triblock copolymers and the diblockcopolymers including the epoxidized isoprene unit with a crosslinkingagent to prepare a crosslinked block copolymer (S50).

First, a step S10 is a step of polymerizing a styrene-based monomer toprepare a styrene-based monomer block, and the kind of styrene-basedmonomer may be the same as the kind of styrene-based monomer for formingthe styrene-based monomer-derived unit described above.

The hydrocarbon solvent is not particularly limited as long as it doesnot react with a polymerization initiator and is usually used in apolymerization reaction, but for example, may be one or more selectedfrom the group consisting of linear or branched hydrocarbon compoundssuch as butane, n-pentane, n-hexane, n-heptane, or isooctane;alkyl-substituted or unsubstituted cyclic hydrocarbon compounds such ascyclopentane, cyclohexane, cycloheptane, methyl cyclohexane, and methylcycloheptane; and alkyl-substituted or unsubstituted aromatichydrocarbon compounds such as benzene, toluene, xylene, and naphthalene.

In addition, the hydrocarbon solvent may include a polar additive foradjusting a vinyl content and improving a polymerization rate, and thepolar additive may be for example, one or more selected from the groupconsisting of tetrahydrofuran, ethyl ether, tetramethyl ethylenediamine, and benzofuran.

In addition, the polymerization initiator is not particularly limited aslong as it is usually used in anionic polymerization, but for example,may be one or more selected from the group consisting of n-butyllithium,sec-butyllithium, tert-butyllithium, methyllithium, ethyllithium,isopropyllithium, cyclohexyllithium, allyllithium, vinyllithium,phenyllithium, and benzyllithium.

Next, a step S20 of polymerizing the styrene-based monomer blockprepared as described above and isoprene to prepare a diblock copolymerincluding a styrene-based monomer-derived unit and an isoprene-derivedunit, may be performed. In the present step, the styrene-based monomerblock and isoprene may be polymerized in the presence of a hydrocarbonsolvent and a polymerization initiator, in which the kinds ofhydrocarbon solvent and polymerization initiator may be the same as thekind of hydrocarbon solvent and polymerization initiator used in thestep S10.

Next, a step of coupling two or more of the diblock copolymers and acoupling agent to prepare a triblock copolymer may be performed. In thisprocess, as described above, a diblock copolymer which does notparticipate in the coupling reaction may remain and be included in thehot melt adhesive composition. That is, the hot melt adhesivecomposition of the present invention may include a block copolymercomposition including a triblock copolymer and a diblock copolymer whichremains without participating in the coupling reaction together.

The coupling agent derives a coupling reaction between the diblockcopolymers, and may be a vinyl group-containing hydrocarbon-basedcompound such as divinylbenzene; an ester-based compound such as diethyladipate and glycidyl methacrylate; a silane compound such asdimethyldichlorosilane, tetrachlorosilane, dimethyldiethoxysilane,dimethyldimethoxysilane, tetraethoxysilane, and tetramethoxysilane, as apolyfunctional coupling agent.

Here, the coupling reaction may be performed, for example, under theconditions of a temperature of 30° C. to 150° C. or 60° C. to 130° C.and a pressure of 0.1 bar to 10 bar or 0.5 bar to 5 bar, and within therange, the coupling reaction may be stably performed.

Subsequently, a step S40 of substituting a part of the isoprene-derivedunit included in the triblock copolymer and the diblock copolymer withan epoxidized isoprene unit may be performed.

This step may be performed by reacting the isoprene-derived unitincluded in the triblock copolymer and the diblock copolymer with amixture of hydrogen peroxide and a carboxylic acid.

The carboxylic acid may be one or more selected from the groupconsisting of a formic acid, an acetic acid, a trifluoroacetic acid, abenzyloxyformic acid, a dinitrobenzoic acid, and a metachlorobenzoicacid.

Here, the mixture of hydrogen peroxide and a carboxylic acid may includethe hydrogen peroxide and the carboxylic acid at a mole ratio of 1:0.8to 1:3, 1:1 to 1:2, or 1:1.2 to 1:1.7. Within the range, epoxidation ofa part of the isoprene-derived unit may be easily performed.

Meanwhile, the mixture of hydrogen peroxide and a carboxylic acid may beused at 0.01 mol to 0.4 mol, specifically 0.02 mol to 0.15 mol, or 0.05mol to 0.1 mol, based on 1 mol of the isoprene-derived unit included inthe triblock copolymer and the diblock copolymer, and within the range,a crosslinking reaction between polymer block chains does not occur toprevent deterioration of physical properties, some isoprene-derivedunits may be easily epoxidized, and an epoxidation ratio may becontrolled to an appropriate range, thereby improving high temperaturestability of the hot melt adhesive composition.

An appropriate range of the epoxidation ratio may be a range in whichthe epoxidized isoprene unit included in the diblock copolymer and thetriblock copolymer is included at 0.5 to 5 parts by weight, based on atotal of 100 parts by weight of the isoprene-derived unit and theepoxidized isoprene unit. Within the range, an excessive decrease orexcessive increase in viscosity during storage of the hot melt adhesivecomposition at a high temperature for a long time may be prevented.

Next, a step S50 of crosslinking two or more of the diblock copolymersand the triblock copolymers including the epoxidized isoprene unit by acrosslinking agent to prepare a crosslinked block copolymer may beperformed.

Specifically, the step S50 may be performed by adding the crosslinkingagent during a process of blending the blend for a hot melt adhesive andthe block copolymer composition after the step S40. More specifically, atime to add the crosslinking agent may be a time when 70% of an entireperiod of the blending process has passed, 80% has passed, or 85% haspassed from the starting point, that is, a time when 30% of the entireperiod of the blending process has left, 20% has left, or 15% has leftfrom the time of blending completion.

As an example, the blending process may be performed for a total of 1hour to 2 hours, 1.2 hours to 1.8 hours, or 1.4 hours to 1.6 hours, anda time to add the crosslinking agent may be 30 minutes, 15 minutes, or10 minutes before completing the blending process.

Meanwhile, for example, when the crosslinking agent is added at thebeginning of blending of the blend for a hot melt adhesive and the blockcopolymer composition after the step S40, that is, before 50% has passedfrom the starting point, the crosslinking reaction starts too early toform too much of a crosslinked product, and viscosity may be excessivelydecreased or excessively increased during storage of the hot meltadhesive composition at a high temperature for a long time.

The blend for a hot melt adhesive may include one or more selected fromthe group consisting of a tackifier, a plastic oil, and an antioxidant.Specifically, the blend for a hot melt adhesive may include all of thetackifier, the plastic oil, and the antioxidant.

According to an exemplary embodiment of the present invention, a processof mixing the blend for a hot melt adhesive at 100 to 250° C., 120 to200° C., or 150 to 180° C. may be further performed, before blending theblend for a hot melt adhesive and the block copolymer composition afterthe step S40.

The crosslinking agent is as described above, and may be used at a moleratio of 0.1 to 1 or 0.3 to 0.7 relative to 1 mol of the epoxidizedisoprene unit included in the block copolymer. Within the range, anexcessive decrease or increase in viscosity during storage of the hotmelt adhesive composition at a high temperature for a long time may beprevented.

Hereinafter, the present invention will be described in more detail bythe Examples. However, the following Examples are provided forillustrating the present invention. It is apparent to a person skilledin the art that various modifications and alterations may be madewithout departing from the scope and spirit of the present invention,and the scope of the present invention is not limited thereto.

EXAMPLES Comparative Example 1

<Preparation of Block Copolymer Composition>

A 10 L reactor substituted with argon (Ar) was set at a temperature of50° C. and a pressure of 1.0 bar, and cyclohexane (5000 g) and styrene(110 g) were added to the reactor and the mixture was stirred. Afterstirring for 10 minutes, n-butyllithium (25 g) was added to initiatepolymerization. 15 minutes after a polymerization temperature of astyrene monomer reached a highest temperature, an isoprene monomer (558g) was added to perform polymerization. 10 minutes after apolymerization temperature of isoprene reached a highest temperature,dimethyldichlorosilane (1.0 g) as a coupling agent was added. 10 minutesafter adding the coupling agent, methanol as a polymerization terminatorwas added to complete polymerization, thereby preparing a compositionincluding a diblock copolymer and a triblock copolymer. After stirring10 minutes, an antioxidant was added. Finally, distilled water was addedto a glass reactor equipped with a stirrer, the temperature wasmaintained at 90° C. by a circulator, and a polymerized product wasslowly added using a dropping funnel with stirring to removecyclohexane. Produced crumbs were dried at a low temperature to preparea block copolymer composition including a diblock copolymer and atriblock copolymer.

<Preparation of Hot Melt Adhesive Composition>

Kixx Process 600 (GS Caltex) which is a white mineral oil as a plasticoil, SU100 (kolon) as a tackifier, and Irganox 1010 as an antioxidantwere added to a 1 L glass beaker, the glass beaker was fixed to aheating mantle at 160° C., stirring was performed at 80 rpm, and after atemperature inside the beaker reached 160° C., stirring was furtherperformed at a higher speed of 100 rpm.

The block copolymer composition prepared in Comparative Example 1 wasslowly added dropwise thereto, and stirring was performed at a speed of100 rpm for 1.5 hours to completely dissolve the block copolymercomposition, thereby preparing a hot melt adhesive composition.

Comparative Example 2

A hot melt adhesive composition was prepared in the same manner as inComparative Example 1, except that after the block copolymer compositionincluding the diblock copolymer and the triblock copolymer was prepared,a mixture of hydrogen peroxide and a formic acid was added, the mixturewas reacted with a part of an isoprene-derived unit included in thediblock copolymer and the triblock copolymer at 70° C. for 2 hours,stirring was performed for 10 minutes, and then sodiumdimethyldithiocarbamate hydrate (SDD) as a reaction terminator and anantioxidant were added. Here, the hydrogen peroxide and the formic acidwas used at 0.035 mol as a total amount of the formic acid and thehydrogen peroxide, based on 1 mol of isoprene used, and the hydrogenperoxide and the formic acid were used at a mole ratio of 1:1.5.

Comparative Example 3

A hot melt adhesive composition was prepared in the same manner as inComparative Example 2, except that the formic acid and the hydrogenperoxide were used at 0.07 mol as a total amount of the formic acid andthe hydrogen peroxide, based on 1 mol of isoprene used.

Comparative Example 4

A hot melt adhesive composition was prepared in the same manner as inComparative Example 2, except that the formic acid and the hydrogenperoxide were used at 0.175 mol as a total amount of the formic acid andthe hydrogen peroxide, based on 1 mol of isoprene used.

Comparative Example 5

A hot melt adhesive composition was prepared in the same manner as inComparative Example 2, except that the formic acid and the hydrogenperoxide were used at 0.35 mol as a total amount of the formic acid andthe hydrogen peroxide, based on 1 mol of isoprene used.

Comparative Example 6

A hot melt adhesive composition was prepared in the same manner as inComparative Example 3, except that the same moles of polyethylene glycol(PEG) as the moles of an epoxidized isoprene unit included in thetriblock copolymer and the diblock copolymer prepared in ComparativeExample 3 were added ([epoxy]/[PEG]=1) to crosslink a block copolymercomposition to prepare a block copolymer composition including acrosslinked block copolymer, which was used to prepare a hot meltadhesive composition.

Experimental Example 1

A diblock copolymer content, a styrene content, a vinyl content, a TSVviscosity, and an epoxidized isoprene unit content of each of the blockcopolymer compositions including the diblock copolymer and the triblockcopolymer prepared in the above Comparative Examples were analyzed andare shown in the following Table 1.

1) Diblock Copolymer Content

The diblock copolymer content included in the block copolymercomposition was expressed as a part by weight based on a total of 100parts by weight of the diblock copolymer and the triblock copolymer. Thediblock copolymer content was measured by GPC using an instrumentincluding Waters 2707 autosampler, Waters 2414 Refractive indexdetector, and Waters 1515 Isocratic HPLC pump. Tetrahydrofuran (FisherT425-4) was used as a development solvent for GPC, and a sample wasprepared by complete dissolution using a shaker. The thus-preparedsample was added using an autosampler, and an isocratic flow was 1ml/min. A column temperature was 40° C. both inside and outside. A parthaving a smaller molecular weight of two peaks of a GPC phase wasanalyzed and measured.

2) Styrene Content

A total content of a styrene monomer-derived unit based on a total of100 parts by weight of the diblock copolymer and the triblock copolymerwas measured and expressed as a part by weight. Analysis was performedusing Varian VNMRS 500 Mhz NMR, and 1,1,2,2-tetrachloroethane D2available from Cambridge Isotope was used as a solvent. A styrenecontent was determined by an area value measured by integrating peaks at7.4 to 6.0 ppm in NMR.

3) Toluene Solution Viscosity (TSV)

The block copolymer composition was dissolved in toluene at aconcentration of 25 wt % and the viscosity was measured using a rotaryviscometer in a thermostat maintained at 25° C.

4) Vinyl Content

A vinyl content in the diblock copolymer and the triblock copolymer wasmeasured by a 500 Mhz NMR device available from Varian. The vinylcontent was expressed as a wt % based on the total weight of the diblockcopolymer and the triblock copolymer.

5) Epoxidized Isoprene Unit Content

The epoxidized isoprene unit content included in the diblock copolymerand the triblock copolymer was measured as a content based on a total of100 parts by weight of the isoprene-derived unit and the epoxidizedisoprene unit.

Analysis was performed using Varian VNMRS 500 Mhz NMR, and1,1,2,2-tetrachloroethane D2 available from Cambridge Isotope was usedas a solvent. A functionalized isoprene content was determined as anarea value measured by integrating doublet peaks near 2.5 to 3.0 ppm.

TABLE 1 Diblock copolymer Styrene Epoxy content content Vinyl TSVcontent (parts by (part by content viscosity (part by Classificationweight) weight) (wt %) (cst) weight) Comparative 19.0 15.0 10.4 1225 0Example 1 Comparative 19.0 15.0 10.4 1225 1 Example 2 Comparative 19.015.0 10.4 1225 2 Example 3 Comparative 19.0 15.0 10.4 1225 5 Example 4Comparative 19.0 15.0 10.4 1225 10 Example 5

Example 1

<Preparation of Block Copolymer Composition>

A block copolymer composition including the diblock copolymer and thetriblock copolymer was prepared in the same manner as in ComparativeExample 3.

<Preparation of Hot Melt Adhesive Composition>

Kixx Process 600 (GS Caltex) which is a white mineral oil as a plasticoil, SU100 (kolon) as a tackifier, and Irganox 1010 as an antioxidantwere added to a 1 L glass beaker, the glass beaker was fixed to aheating mantle at 160° C., stirring was performed at 80 rpm, and after atemperature inside the beaker reached 160° C., stirring was furtherperformed at a higher speed of 100 rpm.

The block copolymer composition prepared in Example 1 was slowly addeddropwise thereto, and stirring was performed at a speed of 100 rpm for1.5 hours to completely dissolve the block copolymer composition,thereby preparing a hot melt adhesive composition. Here, the same molesof polyethylene glycol (PEG) as the moles of the epoxidized isopreneunit included in the diblock copolymer and the triblock copolymerprepared in Example 1 ([epoxy]/[PEG]=1) were added 10 minutes beforestirring of the block copolymer composition of Example 1 was completedto crosslink the block copolymer composition of Example 1, therebypreparing a hot melt adhesive composition including a crosslinked blockcopolymer.

Example 2

A hot melt adhesive composition including a crosslinked block copolymerwas prepared in the same manner as in Example 1, except that an amountof polyethylene glycol used was used at a mole ratio of 0.5 relative tothe moles of the epoxidized isoprene unit.

Example 3

A hot melt adhesive composition including a crosslinked block copolymerwas prepared in the same manner as in Example 1, except that an amountof polyethylene glycol used was used at a mole ratio of 0.33 relative tothe moles of the epoxidized isoprene unit.

Example 4

A hot melt adhesive composition including a crosslinked block copolymerwas prepared in the same manner as in Example 1, except that ethyleneglycol was used instead of polyethylene glycol.

Example 5

A hot melt adhesive composition including a crosslinked block copolymerwas prepared in the same manner as in Example 1, except that the blockcopolymer composition prepared in Comparative Example 4 was used.

Comparative Example 7

A hot melt adhesive composition including a crosslinked block copolymerwas prepared in the same manner as in Example 1, except that the blockcopolymer composition prepared in Comparative Example 5 was used.

Comparative Example 8

A hot melt adhesive composition was prepared in the same manner as inExample 1, except that the block copolymer composition prepared inComparative Example 1 was used.

<Preparation of Adhesive Membrane>

The hot melt adhesive compositions prepared in the above Examples andComparative Examples were melted on a roll of a 120° C. hot melt coaterfor 5 minutes, and the roller of the hot melt coater was passed throughso that a thickness of an adhesive layer was 50 μm, to coat thecomposition on a PET film, thereby preparing an adhesive membrane.

Experimental Example 2

A softening point, an adhesive property, viscosity, peel strength, and aviscosity change rate of the hot melt adhesive compositions prepared inthe above Examples and Comparative Examples were measured, and theresults are shown in Tables 2 and 3.

1) Softening Point

A sufficient amount of the hot melt adhesive composition was added to aring, using an automatic softening point analyzer RB 365G Model andallowed to stand for 1 hour, and then a ball (diameter: 9.525 mm,weight: 3.5 g) was placed thereon. A sample was heated at a rate of 5°C./min, and a temperature when the ball descended by 1 inch was measured(related standard: ASTM D36).

2) Adhesive Property

The adhesive property of the adhesive membrane prepared above wasmeasured using LT-1000 loop tack tester. An adhesive membrane sample wascut into a size of a width of 1 inch and a length of 150 mm, folded inhalf, and fixed to a measuring instrument holder at room temperature,and adhesive strength when the sample was attached to a metal plate andthen detached (related standard: ASTM D 6195B).

3) Peel Strength

The adhesive strength of the adhesive membrane prepared above wasmeasured in a manner of 180°-peel, using a texture analyzer (TA). Theadhesive membrane sample was cut into a size of a width of 1 inch and alength of 150 mm, and the peel strength was measured at a speedcondition of 0.3 m/min at room temperature (related standard: ASTMD1876).

4) Viscosity Change Rate

About 10 g of the hot melt adhesive composition was added to a samplechamber, and a viscosity at 180° C. was measured for 30 minutes, using aBrookfield viscometer (DV2+ Model, Spindle Number 27). Thereafter, thehot melt adhesive composition was allowed to stand at 180° C. for 24hours, and then the viscosity was measured in the same manner, therebymeasuring a viscosity at 180° C. (related standard: ASTM D4402).

TABLE 2 Example Example Example Example Example 1 2 3 4 5 Epoxy content2 2 2 2 5 (part by weight) Crosslinking agent 1 0.5 0.33 1 1 additionamount (mole ratio) Softening point (° C.) 83.7 83.3 82.9 83.5 83.3Adhesive property 1990 1998 1989 1994 2001 (g/in²) (loop tack) Peelstrength (g/in) 1.089 1.090 1.088 1.089 1.098 (180° peel strength)Initial viscosity (cps) 5483 5479 5472 5473 5600 (180° C., 0 h)Viscosity after 3850 4223 4271 3660 5994 24 hours (cps) (180° C., 24 h)

TABLE 3 Comp. Comp. Comp. Comp. Comp. Comp. Comp. Comp. Ex. 1 Ex. 2 Ex.3 Ex. 4 Ex. 5 Ex. 6 Ex. 7 Ex. 8 Epoxy content 0 1 2 5 10 2 10 0 (part byweight) Crosslinking agent 0 0 0 0 0 1 0 1 addition amount (Mole ratio)Softening point (° C.) 82.8 82.4 83.4 83.1 83.8 — 84.1 87.7 Adhesiveproperty 1973 1994 1985 1997 2003 — 2006 1975 (g/in²) (loop tack) Peelstrength (g/in) 1.041 1.072 1.081 1.088 1.095 — 1.102 1.051 (180° peelstrength) Initial viscosity (cps) 5463 5350 5471 5590 5687 — 5699 5470(180° C., 0 h) Viscosity after 1425 1475 1590 1775 1890 — 6523 1430 24hours (cps) (180° C., 24 h)

As confirmed in Tables 2 and 3, it was confirmed that the Examples ofthe present invention in which a part of the isoprene monomer-derivedunit included in the diblock copolymer and the triblock copolymer issubstituted with the epoxidized isoprene-derived unit, and furthermore,during preparation of the hotmelt adhesive composition, a specificcrosslinking agent is added to the blending process of the blend for ahot melt adhesive (tackifier, plastic oil, and antioxidant) and theblock copolymer composition including the epoxidized isoprene-derivedunit (including the diblock copolymer and the triblock copolymer) toinclude the crosslinked block copolymer in which two or more of thediblock copolymers and the triblock copolymers are crosslinked, wereexcellent in terms of the adhesive strength with an adherend and thepeel strength while maintaining a high softening point. In addition, itwas found that since the property of maintaining viscosity duringstorage at a high temperature was improved, the compositions of theExamples were suitable for use as an adhesive (Examples 1 to 5).

However, the hot melt adhesive composition having no epoxidizedisoprene-derived unit (Comparative Example 1) and the hot melt adhesivecomposition including the epoxidized isoprene-derived unit but nocrosslinked block copolymer crosslinked with a specific crosslinkingagent (Comparative Examples 2 to 5) had poor peel strength and rapidlydecreased viscosity during storage at a high temperature, and thus, wereinappropriate for use as a high temperature hot melt adhesive.

Furthermore, in the case in which the crosslinked block copolymercrosslinked with a specific crosslinking agent was included but theepoxidized isoprene-derived unit is excessively included (ComparativeExample 7), viscosity rather increased during storage at a hightemperature.

In addition, in the case in which though the epoxidized isoprene-derivedunit was included and the block copolymer crosslinked with a specificcrosslinking agent was included, the time to add the specificcrosslinking agent was before preparation of the hot melt compositionand after epoxidation (Comparative Example 6), it was confirmed that theblock copolymer composition including the crosslinked block copolymercrosslinked by polyethylene glycol (PEG) was not dissolved in the blendfor a hot melt adhesive (tackifier, plastic oil, and antioxidant) duringpreparation of the hot melt adhesive composition, and thus, it wasimpossible to prepare the hot melt adhesive composition.

In addition, in the case in which a specific crosslinking agent wasadded to perform crosslinking when the diblock copolymer and thetriblock copolymer including no epoxidized isoprene-derived unit wereprepared into the hot melt adhesive composition (Comparative Example 8)also, it was confirmed that the peel strength was poor as compared withthe Examples, and viscosity maintenance ability during storage at a hightemperature was significantly deteriorated.

1. A hot melt adhesive composition comprising: a diblock copolymerincluding a styrene-based monomer-derived unit and a conjugateddiene-based monomer-derived unit; a triblock copolymer which is acoupled polymer of the diblock copolymer; and a crosslinked blockcopolymer including a crosslinking agent-derived crosslinked partcrosslinked with two or more of the diblock copolymers and the triblockcopolymers, wherein the conjugated diene-based monomer-derived unitincludes an isoprene-derived unit and an epoxidized isoprene unitrepresented by the following Chemical Formula 1:


2. The hot melt adhesive composition of claim 1, wherein the epoxidizedisoprene unit included in the hot melt adhesive composition is includedfrom 0.5 to 5 parts by weight, based on a total of 100 parts by weightof the isoprene-derived unit and the epoxidized isoprene unit.
 3. Thehot melt adhesive composition of claim 1, wherein the styrene-basedmonomer-derived unit included in the hot melt adhesive composition isincluded from 10 to 20 parts by weight, based on a total of 100 parts byweight of the diblock copolymer and the triblock copolymer.
 4. The hotmelt adhesive composition of claim 1, wherein the diblock copolymer isincluded a from 15 to 25 parts by weight, based on a total of 100 partsby weight of the diblock copolymer and the triblock copolymer.
 5. Thehot melt adhesive composition of claim 1, wherein the crosslinkingagent-derived crosslinked part is one or more selected from the groupconsisting of polyalkylene glycol and ethylene glycol.
 6. The hot meltadhesive composition of claim 1, further comprising a blend for a hotmelt adhesive, wherein the blend is one or more selected from the groupconsisting of a tackifier, a plastic oil, and an antioxidant.
 7. Amethod of preparing a hot melt adhesive composition, comprising:polymerizing a styrene-based monomer in the presence of a hydrocarbonsolvent and a polymerization initiator to prepare a styrene-basedmonomer block; polymerizing the styrene-based monomer block and isopreneto prepare a diblock copolymer including a styrene-based monomer-derivedunit and an isoprene-derived unit; coupling two or more of the diblockcopolymers and a coupling agent to prepare a triblock copolymer, therebypreparing a block copolymer composition including the triblock copolymerand the diblock copolymer; reacting a part of the isoprene-derived unitincluded in the diblock copolymer and the triblock copolymer and amixture of hydrogen peroxide and a carboxylic acid to substitute a partof the isoprene-derived unit with an epoxidized isoprene unit; andcrosslinking two or more of the triblock copolymers and the diblockcopolymers including the epoxidized isoprene unit with a crosslinkingagent to prepare a crosslinked block copolymer.
 8. The method of claim7, wherein the hydrogen peroxide and the carboxylic acid is used at 0.01mol to 0.4 mol, based on 1 mol of the isoprene-derived unit included inthe diblock copolymer and the triblock copolymer.
 9. The method of claim7, wherein the carboxylic acid is one or more selected from the groupconsisting of a formic acid, an acetic acid, a trifluoroacetic acid, abenzyloxyformic acid, a dinitrobenzoic acid, and a metachlorobenzoicacid.
 10. The method of claim 7, wherein the mixture of the hydrogenperoxide and the carboxylic acid includes the hydrogen peroxide and thecarboxylic acid at a mole ratio of 1:0.8 to 1:3.
 11. The method of claim7, wherein the epoxidized isoprene unit included in the diblockcopolymer and the triblock copolymer is included from 0.5 to 5 parts byweight, based on a total of 100 parts by weight of the isoprene-derivedunit and the epoxidized isoprene unit.
 12. The method of claim 7,wherein the crosslinking two or more of the triblock copolymers and thediblock copolymers is performed by adding the crosslinking agent duringa process of blending a blend for a hot melt adhesive and the blockcopolymer composition.
 13. The method of claim 12, wherein the blend forthe hot melt adhesive includes one or more selected from the groupconsisting of a tackifier, a plastic oil, and an antioxidant.
 14. Themethod of claim 7, wherein the crosslinking agent is used at a moleratio of 0.1 to 1 relative to 1 mol of the epoxidized isoprene unitincluded in the diblock copolymer and the triblock copolymer.
 15. Themethod of claim 7, wherein the crosslinking agent is one or moreselected from the group consisting of polyalkylene glycol and ethyleneglycol.